Allow 2 point versions in images:

We only use 2 points X.Y always unless there is really a patch which is extremely uncommon.
Developers choose the X and tooling chooses the Y. That is the developers only ever have to make a simple decision did I break it or not.

* these are still semver but just treat the patch as optional
* add tests for various combinations of updates

internal/policy/semver.go

@@ -69,7 +69,7 @@ func shouldUpdate(spt SemverPolicyType, matchPreRelease bool, current, new strin
 	}
 
 	parts := strings.SplitN(new, ".", 3)
-	if len(parts) != 3 {
+	if len(parts) != 2 && len(parts) != 3 {
 		return false, ErrNoMajorMinorPatchElementsFound
 	}
 

internal/policy/semver_test.go

@@ -47,6 +47,16 @@ func Test_shouldUpdate(t *testing.T) {
 			want:    false,
 			wantErr: false,
 		},
+		{
+			name: "minor increase - 2 points, policy all",
+			args: args{
+				current: "1.4",
+				new:     "1.5",
+				spt:     SemverPolicyTypeAll,
+			},
+			want:    true,
+			wantErr: false,
+		},
 		{
 			name: "minor increase, policy major",
 			args: args{
@@ -77,6 +87,26 @@ func Test_shouldUpdate(t *testing.T) {
 			want:    true,
 			wantErr: false,
 		},
+		{
+			name: "patch release, policy patch",
+			args: args{
+				current: "1.4",
+				new:     "1.4.6",
+				spt:     SemverPolicyTypePatch,
+			},
+			want:    true,
+			wantErr: false,
+		},
+		{
+			name: "minor and patch release, policy patch",
+			args: args{
+				current: "1.4",
+				new:     "1.5.6",
+				spt:     SemverPolicyTypePatch,
+			},
+			want:    false,
+			wantErr: false,
+		},
 		{
 			name: "patch decrease, policy patch",
 			args: args{
@@ -87,6 +117,16 @@ func Test_shouldUpdate(t *testing.T) {
 			want:    false,
 			wantErr: false,
 		},
+		{
+			name: "2 points minor change, policy patch",
+			args: args{
+				current: "1.4",
+				new:     "1.5",
+				spt:     SemverPolicyTypePatch,
+			},
+			want:    false,
+			wantErr: false,
+		},
 		{
 			name: "patch AND major increase, policy patch",
 			args: args{
@@ -117,6 +157,16 @@ func Test_shouldUpdate(t *testing.T) {
 			want:    true,
 			wantErr: false,
 		},
+		{
+			name: "minor increase 2 points, policy minor",
+			args: args{
+				current: "1.4",
+				new:     "1.5",
+				spt:     SemverPolicyTypeMinor,
+			},
+			want:    true,
+			wantErr: false,
+		},
 		{
 			name: "patch increase, policy minor",
 			args: args{